Conventionally, an emission type electronic display device includes an electroluminescence display (hereinafter, referred to as an ELD). A constituent element of ELD includes such as an inorganic electroluminescent element and an organic electroluminescent element (hereinafter, referred to as an organic EL element).
An organic electroluminescent element is an element provided with a constitution comprising an emission layer containing a emitting substance being sandwiched with a cathode and an anode, and an exciton is generated by an electron and a positive hole being injected into the emission layer to be recombined, resulting emission utilizing light release (fluorescence-phosphorescence) at the time of deactivation of said exciton; the emission is possible at a voltage of approximately a few to a few tens volts, and an organic electroluminescent element is attracting attention with respect to such as superior viewing angle and high visual recognition due to a self-emission type as well as space saving and portability due to a completely solid element of a thin layer type.
In recent years, an organic EL element which utilizes phosphorescence from an excited triplet has been reported from Princeton University (refer to Non patent document 1), researches on materials exhibiting phosphorescence at room temperature have come to be active (refer to Non patent document 2.) Since the upper limit of internal quantum efficiency becomes 100% by utilization of an excited triplet, which is principally 4 times of the case of an excited singlet, it may be possible to achieve almost the same ability as a cooled cathode ray tube to attract attention also for an illumination application. For example, in such as, many compounds mainly belonging to heavy metal complexes such as iridium complexes have been synthesized and studied (refer to Non patent document 3 and Patent document 1.)
Currently, an increase in light emission efficiency and an extension of operating life of organic EL elements, utilizing phosphorescent emission, have been investigated (refer, for example, to Patent Documents 2 and 3). With regard to green light emission, its external light emission efficiency has reached approximately 20% which is the theoretical maximum. On the other hand, light emission of the other colors has not resulted in sufficient efficiency and their improved efficiency has been sought. Specifically, an element which results in a high efficiency of blue light emission has been sought.
On the other hand, of organic light emitting elements, an element, which achieves light emission of high luminance, is one which is constituted by lamination of organic materials produced via vacuum deposition. In view of simplification of production processes, workability, and a larger area, element preparation based on coating systems is hereby disclosed (refer to Patent Document 4).
However, conventional organic electroluminescent elements have further been required to minimize voltage rise when driven at a low voltage and formation of dark spots, and to improve storage stability at high temperature and high humidity.    Patent Document 1: International Patent Publication Open to Public Inspection No. 04/085450 Pamphlet    Patent Document 2: Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) No. 2002-100476    Patent Document 3: JP-A No. 2002-117978    Patent Document 4: JP-A No. 2002-299061    Non-Patent Document 1: M. A. Baldo et al., Nature, Volume 395, pages 151-154 (1998)    Non-Patent Document 2: M. A. Baldo et al., Nature, Volume 403, No. 17, pages 750-753 (2000)    Non-Patent Document 3: S. Lamansky et al., J. Am. Chem. Soc., Volume 123, page 4,304 (2001).